In a large skillet, heat the olive oil over medium heat.
Add the onion and cook for 5-6 minutes, until softened.
Add the garlic and cumin and cook for about 30 seconds, until fragrant.
Add the black beans and broth or water to the skillet and cook for 5-6 minutes, until warmed through.
Add lime juice and season with salt and pepper, to taste.
If desired, top with cilantro and queso fresco.
